Polyvinyl chloride (PVC) is a kind of widely used plastics. The global PVC output can reach 50 million tons per year, and the waste PVC produced each year can reach 10 million tons. How to recycle it is not only an economic problem, but also an environmental problem. The bonding of waste PVC and a metal sheet to form a plastic-steel composite material using the metal as the panel has wide applicability. If the adhesive for bonding is an environment-friendly hot-melt adhesive, the aforementioned two problems related to waste PVC can be solved at the same time, which not only brings in great economic effects, but also has a positive effect on environmental protection.
At present, the bonding of plastics and metals is mainly implemented by direct bonding by using liquid adhesives such as epoxy adhesives and polyurethane adhesives, and the liquid adhesives contain volatile substances which can easily pollute the environment, and are not convenient for manufacturing operations. The hot-melt adhesive is free of solvents, thus, does not pollute the environment, is convenient for manufacturing operations and is beneficial to large-scale rapid operation of the factory.
The patent CN101792641A discloses an adhesive for an aluminum alloy and a PVC film, which is a fast-curing adhesive; and the solvent drying procedure of the adhesive is shortened, but the storage time of the adhesive is shorter, which is inconvenient for practical applications. The patent CN103059792B discloses a polyester elastomer hot-melt adhesive for bonding a polar polymer and a metal material and a preparation method thereof; however, this hot-melt adhesive has low bonding properties for PVC and poor water resistance. The patent CN103756577A discloses a PVC/metal-bonding hot-melt adhesive film and a preparation method thereof; however, the hot-melt adhesive has short bonding and attachment effectiveness for metals, can easily become unglued from the metals, and has poor overall peel strength. The patent CN103045111B discloses a copolyester-based hot-melt adhesive, which can be used for bonding metals and polar materials, but has obvious defects; and it can be seen from the embodiments that the application temperature of the hot-melt adhesive disclosed in this invention is 138° C., but the heat resistance of PVC is poor, and the bonding at the temperature of 138° C. is most likely to cause deformation of the PVC.
In conclusion, the bonding properties of the existing hot-melt adhesives for metals and PVC plastics cannot satisfy the demands in the aspect of practical applications. The development of a novel hot-melt adhesive, which is specially used to bond metals and PVC plastics, has become an urgent problem to be solved.